Re: What happens when I call NSMakeCollectable on a CFArrayRef?

FROM : Andrew Thompson
DATE : Sun Jan 20 18:42:16 2008

On Jan 19, 2008, at 6:17 PM, Clark Cox wrote:

> On Jan 19, 2008 2:56 PM, Andrew Thompson <<email_removed>> wrote:

>> I want to call a Core function that returns a CFArrayRef and make the
>> result garbage collectable.
>> The CFArray contains CFStrings...
>>
>> Is this pattern OK?
>>
>> -(NSArray *) doFoo {
>>  return NSMakeCollectable(CFCopyFoo(someArgs));
>> }
>>
>> Where CFCopyFoo returns a new CFArray containing copied CFStrings.

>
> This will make the array collectable, but will do nothing to the items
> contained therein; the contents are still reference counted. However,
> this is most likely what you want anyway (Just as in pre-GC code, when
> an item is removed from the array, or the array itself is
> collected/deallocated, the item will have its reference count
> decremented, and will be deallocated if that was the last remaining
> reference).


That's more or less what I figured, thanks.

>

>> Or do I have to iterate over the array and call NSMakeCollectable on
>> each item in it?

>
> That would do something completely different, and would not be a good
> idea (it would be akin to calling CFRelease on each of the items).



Really? I would have thought that since each is in the array, so long 
as the array isn't garbage then each string is referenced and is 
therefore also not garbage and will stick around as long as the array 
does?

So on balance - if the strings are going to be left in the array, then 
making the array collectable is enough - once it becomes garbage the 
strings will be released too.

Conversely if I intend to pull the strings out of the array and start 
passing them around to other objects in my program, I likely want to 
take the extra trouble to make each one collectable, otherwise I might 
forget to release them and they'll leak.


AndyT (lordpixel - the cat who walks through walls)
A little bigger on the inside

   (see you later space cowboy, you can't take the sky from me)